This invention relates to a non-resonating type knock sensor adapted to be secured to an internal combustion engine for detecting the occurrence of knocking of the engine.
There is a known non-resonating type knock sensor which comprises a synthetic resin case adapted to be secured to a suitable portion of an internal combustion engine, an annular piezoelectric element fixedly disposed within the case and having a pair of electrodes on both sides thereof, a pair of terminal pins each in electrical contact with respective electrodes, and a cylindrical connector wall extending radially outward from the piezoelectric element for surrounding the terminal pins (Japanese Published Unexamined Patent Application (Tokkyo Kokai) No. 61-153,530).
With such a non-resonating type knock sensor, the vibration from knocking imposes a compressive strain on the piezoelectric element proportionally to the knocking frequency so that a piezoelectric voltage signal is generated from the piezoelectric element in accordance with the vibration. The output signal is picked up by the lead wire and is transmitted outside of the sensor from the connector pins through a coupler connected to the connector.
The present inventors have found that the knock sensor of the non-resonating type tends to generate noises so that the knocking of the engine is failed to be precisely detected.